This is also valid in American. In fact, the prototype answer given is not grammatical English.
Yes, I was marked wrong for this. The translation given is wrong as it means that there is no physical obstruction rather than costing nothing
I changed my answer from 'admission' (fee implied); to 'entry' after checking the 'hover'. Now -- problem: if the entry or entrance is free, does it mean free of obstacles or encumbrances?? One can get through without physical difficulties?
In this case, where the phrase is "The entrance is completely free," or "L'entrata è completamente gratuita," free means without price. The word for free of obstacles is something closer to libero or libera.